Acoustic data transmission, telemetry and underwater communication systems

A method for acoustic communications, the method comprising:

• defining a limited set of coded signals, each of the coded signals being selected for low cross-correlation with other coded signals in the limited set, wherein defining the limited set of coded signals comprises defining each of the coded signals as a binary sequence, wherein the limited set of coded signals defines 2N+1 or fewer such binary sequences, wherein:
• N is a positive integer;
• and
• each of the binary sequences has a period of 2N−1 or more;
• defining a set of messages, wherein each message is associated with a selected one of the coded signals in the limited set;
• identifying one of the messages for transmission;
• and
• transmitting the coded signal associated with the identified message, via a subsurface acoustic medium.

A subsurface craft comprising:

• a hull and propulsion system adapted for navigation through a subsurface acoustic medium;
• an acoustic transducer deployed with the hull, the acoustic transducer configured for communicating signals via the acoustic medium;
• a controller in communication with the acoustic transducer, the controller comprising:
• a signal programmer adapted for defining a limited set of coded signals, each of the coded signals selected for low cross-correlation with other coded signals in the limited set;
• and
• a signal encoder adapted for defining a set of messages, wherein each message is associated with a selected one of the coded signals in the limited set;
• and
• an interface for identifying one of the messages for transmission, wherein the acoustic transducer is configured to transmit the coded signal associated with the identified message via the subsurface acoustic medium.